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An associative memory module for data-flow processors
Başlık:
An associative memory module for data-flow processors
Yazar:
Patterson, John William, author.
ISBN:
9780438053601
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (360 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: D. C. Gilles.
Özet:
This thesis describes a novel form of associative memory considered suitable for inclusion in packet communication architectures and in particular in data-flow computer architectures. Packet communication architectures typically consist of active elements connected together by communications paths which include buffer regions from which the active elements select packets to work on and to which they send their result packets. The communication paths permit packets to return to their point of origin, either in something like their original form, or as acknowledgement messages. The machine's activities are distributed among the active elements so that they can always be busy so long as there are packets for them to work on. Most data-flow machine designs are presented as packet communication architectures. These offer the possibility that the machines' performance, as measured in terms of their throughput of work, can grow linearly with the number of active elements provided. Data-flow machines execute their instructions whenever the instruction operands are available, and this is normally done by forming packets which ultimately include the instruction and its operands. When the packet is completed, the instruction is executed. The original presentation of data-flow machine organization required the use of associative memory to match operands with their instructions, but, because no form of associative memory is known which is well-suited to the requirements of packet communication architectures, all the forms of data-flow machine organization which have been described so far use location-addressed memories to simulate the necessary properties of associative memory. This thesis describes a form of associative memory which satisfies the requirements for packet communication architectures and which could be used to match instructions with operands as well as to provide a general-purpose memory region in data-flow architectures. The form of associative memory described is classified as dynamic, word-serial memory, and is intended to be implemented in one or more modules, each of which is capable of supporting a population of simultaneous accesses, including simultaneous accesses to the same data. Each memory module consists of populations of five resource types, namely memory cells, data entry channels, match channels, readout networks, and restoration networks. Each instance of each resource acts independently of each other and where necessary communicates its requirements to other resources by flagging the data packets it handles to indicate that the packet requires the use of that resource. Associative memories differ from location-addressed memories in the way in which the data elements to be accessed are identified. In associative memories this is done by comparing each data element with a key (and in the form of memory described here, a mask as well) and flagging the elements which satisfy some relation to the key (here, equality of the unmasked bits of the key) as responders. In dynamic memories data elements move past match stations which perform the comparisons. In the form of memory described here, there may be several match stations (referred to as 'match channels'), which can perform different matches at the same time. Under certain conditions, some of the match channels can carry keys intended to match the same data elements, although special arrangements have to be made to regulate this case. Responders to a key-and-mask match may not be unique, so a single access may identify a number of responders. Here, responders are flagged as such, and these flags or tokens indicate to the data exit resources (the readout and restoration networks) that the data is to be read out of memory either destructively, in which case it leaves by the next available readout network, or nondestructively, in which case a copy enters the the next available restoration network and is re-entered into the memory. Data is entered into the memory through data entry channels which also act independently of the other resources. There may be as many data entry channels as are needed to cater for the anticipated flow into the memory. Data entry channels take advantage of the dynamic nature of the memory to perform exchange processes whose cumulative effect, together with that of the restoration networks, is to order data in the memory by frequency of access. When the memory module is full, the least recently accessed data elements are those which are due to be displaced, and it is shown how to take advantage of this to tailor the resources of the module to relate resource availability to resource need. One of the main characteristics of the memory module is that it only requires local decisions to determine what happens to a data packet, and thus the module may be implemented in any technology, fast or slow. Some ways of implementing the module in VLSI circuits are discussed by way of illustration in the further work section of this thesis. To demonstrate the conclusion about decision locality the module is described down to the logic level. It is shown that the module is capable of providing the regular throughput required of packet communication architectures although the time to access a single data set is limited by internal latencies which do not affect the flow rate. In the further work section it is suggested that various forms of the memory module may be used in all parts of a data-flow machine organization, although modification of the original form of memory is required. It is also suggested that the machine can implement various computation cycles other than data-flow computation, and that the machine has a near-linear growth in performance with resources.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684467.1) | 684467-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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